<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
</head>
<body>
<div id="root">
  <input type="text">
  <div></div>
</div>
</body>
<script>
  const input = document.querySelector("input");
  const div = document.querySelector("#root div");
  const data = {
    username:"zhangsan"
  };
  input.value = div.innerText = data.username;
  input.oninput = function(){
    div.innerText = this.value;
  }

</script>
</html>